Everyone knows that NASA studies space; fewer people know that NASA also studies Earth. Since the agency’s creation almost 50 years ago, NASA has been a world leader in space-based studies of our home planet. Our mission has always been to explore, to discover, and to understand the world in which we live from the unique vantage point of space, and to share our newly gained perspectives with the public. That spirit of sharing remains true today as NASA operates 18 of the most advanced Earth-observing satellites ever built, helping scientists make some of the most detailed observations ever made of our world.

In celebration of the deployment of its Earth Observing System, NASA is pleased to share the newest in its series of stunning Earth images, affectionately named the “Blue Marble.” This new Earth imagery enhances the Blue Marble legacy by providing a detailed look at an entire year in the life of our planet. In sharing these Blue Marble images, NASA hopes the public will join with the agency in its continuing exploration of our world from the unique perspective of space.

Enhancements

Blue Marble: Next Generation offers greater spatial detail of the surface and spans a longer data collection period than the original. The original Blue Marble was a composite of four months of MODIS observations with a spatial resolution (level of detail) of 1 square kilometer per pixel. Blue Marble: Next Generation offers a year’s worth of monthly composites at a spatial resolution of 500 meters. These monthly images reveal seasonal changes to the land surface: the green-up and dying-back of vegetation in temperate regions such as North America and Europe, dry and wet seasons in the tropics, and advancing and retreating Northern Hemisphere snow cover. From a computer processing standpoint, the major improvement is the development of a new technique for allowing the computer to automatically recognize and remove cloud-contaminated or otherwise bad data—a process that was previously done manually.

The Blue Marble: Next Generation is a series of images that show the color of the Earth’s surface for each month of 2004 at very high resolution (500 meters/pixel) at a global scale. This image shows South America from September 2004. (NASA image courtesy Reto Stöckli and Robert Simmon)

Blue Marble: Next Generation improves the techniques for turning satellite data into digital images. Among the key improvements is greater detail in areas that usually appear very dark to the satellite (because a large amount of sunlight is being absorbed), for example in dense tropical forests. The ability to create a digital image that provides great detail in darker regions without “washing out” brighter regions, like glaciers, snow-covered areas, and deserts is one of the great challenges of visualizing satellite data. The new version also improves image clarity, and gives highly reflective land surfaces, such as salt flats, a more realistic appearance.

Monthly imagery shows seasonable variability, like the change in Alpine snow-cover from January to July. (NASA images by Reto Stöckli)

Limitations

Those who intend to use the Blue Marble: Next Generation in their own publications or projects should be aware of areas that still require improvement. Areas of open water still show some “noise.” In tropical lowlands, cloud cover during the rainy season can be so extensive that obtaining a cloud-free view of every pixel of the area for a given month may not be possible. Deep oceans are not included in the source data; the creator of the Blue Marble uses a uniform blue color for deep ocean regions, and this value has not been completely blended with observations of shallow water in coastal areas. The lack of blending may, in some cases, make the transition between shallow coastal water and deep ocean appear unnatural. Finally, the data do not completely distinguish between snow and cloud cover in areas with short-term snow cover (less than three or four months). This problem may be resolved in the future through the use of a more sophisticated snow mask.

Data Access

Full-resolution, subsetted, and reduced-resolution files are available on the Blue Marble Next Generation collection on NASA’s Visible Earth.

Improvements to the data-processing algorithms resulted in relatively noise-free images with few artifacts. Dry salt flats, such as the Etosha Pan in Namibia, rendered as water in the original Blue Marble, but are now accurately colored. (NASA images by Reto Stöckli.)

This spectacular blue marble image is the
most detailed true-color image of the entire Earth to date. Using a collection of satellite-based observations,
scientists and visualizers stitched together months of observations of the land surface,
oceans, sea ice, and clouds into a seamless, true-color mosaic of every
square kilometer (.386 square mile) of our planet. These images
are freely available to educators, scientists, museums, and the public. Preview images
and links to full resolution versionsup to 21,600 pixels acrossare
located below.

Much of the information contained in this image came from a single
remote-sensing device-NASAs Moderate Resolution Imaging
Spectroradiometer, or MODIS. Flying over 700 km above the Earth onboard
the Terra satellite, MODIS provides an integrated tool for observing a
variety of terrestrial, oceanic, and atmospheric features of the Earth.
The land and coastal ocean portions of these images are based on
surface observations collected from June through September 2001 and
combined, or composited, every eight days to compensate for clouds that
might block the sensors view of the surface on any single day. Two different types of ocean data were used in these images: shallow water
true color data, and global ocean color (or chlorophyll) data. Topographic shading is based on the GTOPO 30 elevation dataset compiled by the U.S. Geological Surveys
EROS Data Center. MODIS observations of polar sea ice
were combined with observations of Antarctica made by the National
Oceanic and Atmospheric Administrations AVHRR sensorthe Advanced Very
High Resolution Radiometer. The cloud image is a composite of two days of imagery collected in visible
light wavelengths and a third day of thermal infra-red imagery over the poles. Global city lights, derived from 9 months of observations from the Defense Meteorological Satellite Program,
are superimposed on a darkened land surface map.

The 1-kilometer per pixel resolution of these data reveals surprising
details of the Earths surface, from the diversity of color in the Great Salt Lake to deforestation in the Amazon
and the glaciers of the Himalaya.

History of the Blue Marble

The Earth didn’t appear blue in NASA’s first satellite images; rather, the Television Infrared Observation Satellite, known as TIROS, beamed home images in black and white. Still, those earliest images showed that a yet-unproven method of observing the Earth from space would help improve weather forecasts.

Astronaut photographs taken during the Apollo missions provided full-color images of Earth, and fostered a greater awareness of the need to understand our home planet. In 1972, from a distance of about 45,000 km (28,000 mi), the crew of Apollo 17 took one of the most famous photographs ever made of the Earth. This original Blue Marble inspired later images of the Earth compiled from satellite data. In 2000, NASA data visualizers compiled an image of the western hemisphere using data from the National Oceanic and Atmospheric Administration’s GOES-8 and Advanced Very High Resolution Radiometer, and NASA and Orbital Sciences Corporation’s Sea-viewing Wide Field-of-view Sensor.

The first television image of the Earth from space, taken by the Television Infrared Observation Satellite (TIROS-1) on April 1, 1960. (Image by NASA)

In 2002, NASA produced the Blue Marble, the most detailed true-color image of the Earth’s surface ever produced. Using data from NASA’s Terra satellite, scientists and data visualizers stitched together four months of observations of the land surface, coastal oceans, sea ice, and clouds into a seamless, photo-like mosaic of every square kilometer (.386 square mile) of our planet. In October 2005, NASA released a new version of the spectacular image collection that provides a full year’s worth of monthly observations with twice the level of detail as the original. The new collection is called the Blue Marble: Next Generation.

On December 7, 1972, the crew of Apollo 17 changed the way we look at our home planet. This photograph illustrates the Earth as an isolated ecosystem, floating in space. (Astronaut photograph AS17-148-22727 courtesy NASA Johnson Space Center Gateway to Astronaut Photography of Earth)

Like the original, the Blue Marble: Next Generation is a mosaic of satellite data taken mostly from a NASA sensor called the Moderate Resolution Imaging Spectroradiometer (MODIS) that flies board NASA’s Terra and Aqua satellites. Also like its predecessor, the new Blue Marble is available free of charge to educators, scientists, museums, businesses, and the public. The collection includes images that are sized for different media, including Web and print. Users can download images of the entire globe, or just selected regions of interest.

The 2002 Blue Marble featured land surfaces, clouds, topography, and city lights at a maximum resolution of 1 kilometer per pixel. (NASA image by Robert Simmon and Reto Stöckli)